The present invention relates to a microwave heating device and a heating method based on the device and more particularly, to a technique for controlling the temperature of a substance to be heated to a constant value while irradiating the heated substance with microwaves.
Nowadays, the microwave is widely used in a domestic microwave oven for cooking and besides, its use is spread industrially to, for example, gum vulcanization, drying of tea leaves and foodstuffs sterilization. Further, application of the microwave to chemical synthesis process has currently been started and a report has been made, as described in “Microwave-assisted Chemical Process Technology” supervised by Yuji Wada and published by CMC, purporting that in comparison with the conventional heating method, the microwave can be utilized for chemical reactions with more versatility as exemplified by improvements in reaction speed and in addition, patent applications concerning chemical reaction devices utilizing microwaves have already been filed as disclosed in JP-A-2006-188666 and JP P2000-515064A.
In other words, it has been reported that the microwave heating is not based on a heating method using heat transfer from an external heat source as in the case of the conventional heating method but acts directly on molecules of a substance to be heated, thus drastically expediting speedup of heating as compared to the conventional heating method.